Disposable absorbent article

ABSTRACT

An absorbent article that can be a sanitary napkin. The absorbent article comprises a topsheet joined to a backsheet and has an absorbent core material disposed therebetween, the absorbent core material being a fibrous absorbent material exhibiting on one side thereof discrete raised portions. The raised portions define a continuous network of channels, the channels defining a void region adjacent the topsheet of the sanitary napkin.

FIELD OF THE INVENTION

The present invention relates to absorbent cores for disposableabsorbent articles such as sanitary napkins and disposable diapers.

BACKGROUND OF THE INVENTION

Disposable absorbent articles such as disposable diapers and femininehygiene articles are well known in the art. Such articles are designedto absorb exudates from the wearer's body. Disposable absorbent articlestypically have a fluid permeable body contacting layer called atopsheet, a fluid impermeable layer called a backsheet joined to thetopsheet, and an absorbent layer referred to as an absorbent coresandwiched between the topsheet and backsheet. In operation fluidexiting the wearer's body enters the disposable absorbent articlethrough the topsheet and is stored in the absorbent core. The backsheetprevents any excess fluid that is not absorbed from exiting thedisposable absorbent article. For disposable absorbent articles likesanitary napkins intended to be worn with other clothing, the backsheetcan be a garment-facing layer, and typically aids in preventing soilingof the clothing.

Other elements can be included in disposable absorbent articles,including additional absorbent layers having structures designed forcertain functions. For example, a secondary topsheet can be an absorbentlayer placed between the topsheet and the absorbent core, and having astructure designed to wick fluid quickly away from the topsheet and intothe absorbent core. Likewise, multiple layers of absorbent cores can beused, each layer having fluid handling properties designed to securelymove fluid into the absorbent core for secure storage. Additionally,each layer of absorbent core material can itself be a layered orlaminate structure having discrete layers as is known in the art of airlaying webs using multiple air laying heads or beams. In a layeredabsorbent core material, any one discrete layer can comprise a differenttype or blend of fibers with respect to one other discrete layer.

It is known to design absorbent cores having a structure such that fluidmovement from the topsheet toward the backsheet, i.e., away from thewearer's body, is facilitated. For example, fibrous layered absorbentcores in which the capillarity of the fibrous layers is increased witheach layer are known. Likewise, it is known to have layered absorbentcores wherein with each succeeding layer in a direction away from thetopsheet the permeability is decreased. In this manner, fluid enteringthrough the topsheet first encounters a layer having high permeabilityand low capillarity to facilitate quick fluid uptake. From this firstlayer, the fluid can encounter a layer having less permeability andhigher capillarity, such that the fluid continues to move away from thetopsheet, but at a slower rate. This is generally acceptable becauseonce the fluid is away from the wearer's body the rate at which it movesto other portions of the absorbent core is not critical.

In known absorbent cores there is a well-known tradeoff between thepermeability of a material and its capillarity. In general, knownmaterials that are relatively higher in permeability are relativelylower in capillarity, and vice versa. For disposable absorbent articles,in which it is desirable to have both parameters uncoupled, a positivechange in one of these parameters results in a corresponding negativechange in the other. Because permeability directly affects a material'sacquisition rate and capillarity directly impacts the movement of fluiddue to limits in capillary pressure, this tradeoff in properties has, inthe past, resulted in an absorbent core chosen for a balance ofproperties. The necessary tradeoff, however, has resulted in absorbentstructures, including absorbent cores, in which the desired levels ofacquisition rate and effective fluid movement to secure storage cannotbe achieved simultaneously.

Accordingly, it would be desirable to have an absorbent article and anabsorbent core material in which both permeability and capillaritypressure can be maintained at desirable levels simultaneously in anabsorbent core.

Additionally, it would be desirable to have an absorbent article and anabsorbent core material in which the negative aspects of either ofpermeability or capillarity pressure when one or the other is moreoptimized, are minimized.

Further, it would be desirable to have an absorbent article and anabsorbent material in which the tradeoff between permeability andcapillarity pressure is managed such that delivering relatively higherpermeability can be accomplished without a decrease in capillaritypressure.

SUMMARY OF THE INVENTION

An absorbent article that can be a sanitary napkin is disclosed. Theabsorbent article comprises a topsheet joined to a backsheet and has anabsorbent core material disposed therebetween, the absorbent corematerial being a fibrous absorbent material exhibiting on one sidethereof discrete raised portions. The raised portions define acontinuous network of channels, the channels defining a void regionadjacent the topsheet of the sanitary napkin. The discrete raisedportions and the channels define intermediate areas of localizedreductions in web thickness, the intermediate areas having asubstantially different density of basis weight than the discrete raisedportions or the channels. The discrete raised portions may take the formof rib-like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cut-away perspective view of a sanitary napkinembodying the present invention.

FIG. 2 is a schematic representation of a process for mechanicalmodification of web materials through a nip of a pair of inter-meshingrolls.

FIG. 3 is schematic representation of a pair of inter-meshing rolls of aprocess commonly referred to as ring-rolling.

FIG. 4 is an enlarged, fragmentary, cross-sectional view showing theinterengagement of teeth and grooves of respective rolls of aring-rolling apparatus as shown in FIG. 3.

FIG. 5 is an even further enlarged view of a ring-rolling apparatus asshown in FIG. 3 showing several interengaged teeth and grooves with aweb of material therebetween.

FIG. 6 is schematic representation of a pair of inter-meshing rolls of aprocess commonly referred to a SELF process.

FIG. 7 is a schematic representation of a process for modifying a web bythe SELF process.

FIG. 8 is a schematic representation of a web after it has passedbetween a pair of inter-meshing SELF rolls.

FIG. 9 is a pattern that can be produced in an absorbent material bypassing the material between a pair of inter-meshing SELF rolls.

FIG. 10 is a pattern that can be produced in an absorbent material bypassing the material between a pair of inter-meshing SELF rolls.

FIG. 11 is a side view of a roll for use in a micro-SELF process.

FIG. 12 is a perspective representation of roll for use in a micro-SELFapparatus.

FIG. 13 is an enlarged perspective representation of the teeth on amicro-SELF roll.

FIG. 14 is a schematic representation of a rotary knife apparatus (RKA)and process.

FIG. 15 is a portion of one embodiment of a roller of a rotary knifeapparatus, the roller having a plurality of teeth useful for making anapertured web.

FIG. 16 is an enlarged perspective representation of one embodiment ofteeth on the toothed roll of a rotary knife apparatus.

FIG. 17 is a side view of a SELF roll.

FIG. 18 is a cross-sectional view of the roll shown in FIG. 17, takenalong line 18-18.

FIG. 19 is a cross-sectional view of the teeth of the SELF roll shown inFIG. 18.

FIG. 20 is an enlarged side view of the teeth of the roll shown in FIG.17.

FIG. 21 is a flat layout view of an SELF roll having a staggered toothpattern.

FIG. 22 is a cross-sectional view of a portion of the SELF roll shown inFIG. 21, taken along line 22-22.

FIG. 23 is an enlarged plan view of some of the teeth of the SELF rollshown in FIG. 21.

FIG. 24 is a partial perspective view showing one embodiment of teeth onRKA roll.

FIG. 25 is a plan view of the teeth of a RKA roll as shown in FIG. 24.

FIG. 26 is a cross-sectional view of teeth on a RKA roll of FIG. 25taken along line 26-26 of FIG. 25.

FIG. 27 is a cross-sectional view of teeth on a RKA roll of FIG. 24taken along line 27-27 of FIG. 24.

FIG. 28 is a side view of a SELF roll suitable for the presentinvention.

FIG. 29 is a view of the outer surface of the SELF roll shown in FIG.28.

FIG. 30 is a schematic detail of the teeth of the roll shown in FIGS. 28and 29.

FIG. 31 is a partial perspective view showing one embodiment of teeth ona RKA roll.

FIG. 32 is a plan view of a portion of the RKA roll shown in FIG. 31.

FIG. 33 is a partial cross-sectional view of FIG. 32 showing oneembodiment of teeth on a RKA roll.

FIG. 34 is a side view showing the teeth of FIG. 31.

FIG. 35 is a partial perspective view showing one embodiment of teeth ona RKA roll.

FIG. 36 is a plan view of a portion of the RKA roll shown in FIG. 35.

FIG. 37 is a partial cross-sectional view of 37-37 in FIG. 36 showingone embodiment of teeth on a RKA roll.

FIG. 38 is a side view showing the teeth of FIG. 35.

FIG. 39 is a schematic representation of a web of the present invention.

FIG. 40 is a schematic representation of a web of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the invention is an absorbent core having utility asthe fluid storage component of a disposable absorbent article, such as afeminine hygiene article. One embodiment of a feminine hygiene articleof the present invention, a sanitary napkin 10, is shown in perspectiveview in FIG. 1. While the invention is disclosed in FIG. 1 as anembodiment of a sanitary napkin 10, the disclosed features of theinvention can also be useful when incorporated in other feminine hygienearticles, such as incontinence pads and pantiliners. Therefore, thedescription below is in the context of a sanitary napkin, but it isapplicable to feminine hygiene articles in general. Likewise, theabsorbent core of the present invention can find utility in otherdisposable absorbent articles, including disposable diapers, adultincontinent devices, hemorrhoid treatment pads, bandages, and the like.Still further, the structure produced by the methods and apparatusdisclosed herein can find utility in other webs for which surfacetexture of heterogeneous fiber structure is beneficial, such as wipes,scouring pads, dry-mop pads (such as Swiffer® pads), and the like.

Sanitary napkin 10 can be considered in three regions, two end regions12 and 14 each comprising about one-third of the overall length, and amiddle region 16. Sanitary napkin 10 has a body-facing surface (or side)15 that is in contact with the user's body during use and agarment-facing surface (or side) 17 that is in contact with the user'sundergarment during use. In general, each component layer of thesanitary napkin 10 can be said to have a body-facing side and agarment-facing side, the sides being determined by their orientationrelative to the in-use orientation of the article. Sanitary napkin 10has a longitudinal centerline L and a transverse centerline T, thecenterlines being perpendicular to one another in the plane of thesanitary napkin when in a flat out configuration, as shown in FIG. 1. Inone embodiment the sanitary napkin can be generally symmetric about bothcenterlines, while in other embodiments the sanitary napkin can begenerally asymmetric about either centerline. In the embodiment shown inFIG. 1, sanitary napkin 10 is symmetric about the longitudinalcenterline L and symmetric about transverse centerline T. Femininehygiene articles can also be provided with lateral extensions known inthe art as “flaps” or “wings” (not shown in FIG. 1) intended to foldover and cover the panty elastics in the crotch region of the user'sundergarment.

Sanitary napkin 10 can have any shape known in the art for femininehygiene articles, including generally symmetric “hourglass” shaped asshown in FIG. 1, or tapering inwardly from a relatively greatertransverse width in a portion of one of the end regions to a relativelysmaller transverse width at the middle region 16, such that the maximumtransverse width of one end, e.g., end region 12, of the pad is greaterthan the maximum transverse width of the other end, e.g., end region 14.Transverse width is defined herein as the edge-to-edge dimension acrossthe article, measured parallel to the transverse centerline T. Such padscan be described as pear shaped, bicycle-seat shaped, trapezoidalshaped, wedge shaped, or otherwise described in a manner that connotes atwo-dimensional shape having two ends in which one end is larger thanthe other in a maximum width dimension.

Sanitary napkin 10 can have an absorbent core 20 to absorb and storebodily fluids discharged during use. In some embodiments of sanitarynapkins, pantiliners, incontinence pads, or other such devices of thepresent invention, an absorbent core is not necessary, the padconsisting only of a topsheet (that can have some absorbency) and afluid impermeable backsheet. Absorbent core 20 can be formed from any ofthe materials well known to those of ordinary skill in the art. Examplesof such materials include multiple plies of creped cellulose wadding,fluffed cellulose fibers, wood pulp fibers also known as airfelt,textile fibers, a blend of fibers, a mass or batt of fibers, airlaidwebs of fibers, a web of polymeric fibers, and a blend of polymericfibers.

In one embodiment absorbent core 20 can be relatively thin, less thanabout 5 mm in thickness, or less than about 3 mm, or less than about 1mm in thickness. Thickness can be determined by measuring the thicknessat the midpoint along the longitudinal centerline of the pad by anymeans known in the art for doing while under a uniform pressure of 0.25psi. The absorbent core can comprise absorbent gelling materials (AGM),including AGM fibers, as is known in the art.

Absorbent core 20 can be formed or cut to a shape, the outer edges ofwhich define a core periphery 30. The shape of absorbent core 20 can begenerally rectangular, circular, oval, elliptical, or the like.Absorbent core 20 can be generally centered with respect to thelongitudinal centerline L and transverse centerline T. The profile ofabsorbent core 20 can be such that more absorbent is disposed near thecenter of the absorbent article. For example, the absorbent core can bethicker in the middle, and tapered at the edges in a variety of waysknown in the art.

Absorbent core 20 can be an airlaid core of the type disclosed in U.S.Pat. Nos. 5,445,777; or 5,607,414. Absorbent core can comprise a highcapacity and highly absorbent core material of the type generallyreferred to as HIPE foams, such as those disclosed in U.S. Pat. Nos.5,550,167; 5,387,207; 5,352,711; and 5,331,015. In one embodiment, theabsorbent core can have a capacity after desorption at 30 cm of lessthan about 10% of its free absorbent capacity; a capillary absorptionpressure of from about 3 to about 20 cm; a capillary desorption pressureof from about 8 to about 25 cm; a resistance to compression deflectionof from about 5 to about 85% when measured under a confining pressure of0.74 psi; and a free absorbent capacity of from about 4 to 125grams/gram. Each of these parameters can be determined as set forth inU.S. Pat. No. 5,550,167, issued Aug. 27, 1996 to DesMarais. Oneadvantage of utilizing the airlaid or HIPE foam cores as disclosed isthat the absorbent core can be made very thin. For example, an absorbentcore of the present invention can have an average caliper (thickness) ofless than about 3 mm, or less than about 2 mm, and the thickness can beless than about 1 mm.

To prevent absorbed bodily exudates from contacting the wearer'sgarments, sanitary napkin 10 can have a liquid impermeable backsheet 22.Backsheet 22 can comprise any of the materials known in the art forbacksheets, such as polymer films and film/nonwoven laminates. Toprovide a degree of softness and vapor permeability for thegarment-facing side of sanitary napkin 10, backsheet 22 can be a vaporpermeable outer layer on the garment-facing side of the sanitary napkin20. The backsheet 22 can be formed from any vapor permeable materialknown in the art. Backsheet 22 can comprise a microporous film, anapertured formed film, or other polymer film that is vapor permeable, orrendered to be vapor permeable, as is known in the art. One suitablematerial is a soft, smooth, compliant, vapor pervious material, such asa nonwoven web that is hydrophobic or rendered hydrophobic to besubstantially liquid impermeable. A nonwoven web provides for softnessand conformability for comfort, and can be low noise producing so thatmovement does not cause unwanted sound.

To provide for softness next to the body, sanitary napkin 10 can have abody-facing layer, referred to herein as topsheet 26. Topsheet 26 can beformed from any soft, smooth, compliant, porous material which iscomfortable against human skin and through which fluids such as urine orvaginal discharges can pass. Topsheet 26 can comprise fibrous nonwovenwebs and can comprise fibers as are known in the art, includingbicomponent and/or shaped fibers. Bicomponent fibers can comprisepolypropylene (PP) and polyethylene (PE) in known configurations,including core/sheath, side by side, islands in the sea, or pie. Shapedfibers can be tri-lobal, H-shaped in cross section, or any other knowncross-sectional shape. Topsheet 26 can also be a liquid permeablepolymer film, such as an apertured film, or an apertured formed film asis known on sanitary napkins such as Always® brand sanitary napkins.

At least one, and preferably both, of topsheet 26 and backsheet 22define a shape, the edge of which defines an outer periphery 28 of thesanitary napkin 10. In one embodiment, both topsheet 26 and backsheet 22define the sanitary napkin 10 outer periphery 28. The two layers can bedie cut, as is known in the art, for example, after combining all thecomponents into the structure of the sanitary napkin 10 as describedherein. However, the shape of either topsheet 26 or backsheet 22 can beindependently defined.

Disposable absorbent articles can include a lotion, skin careingredients, fragrances, odor control agents, and other components. Inone embodiment, a lotion that can include a skin care composition can beadded by spraying, extrusion or slot coating to a topsheet. The skincare composition can be hydrophilic or hydrophobic, and can have fromabout 0.001% to about 0.1% by weight of hexamidine, from about 0.001% toabout 10% by weight of zinc oxide, from about 0.01% to about 10% byweight of niacinamide, and a carrier such as petrolatum. The lotion caninclude glycols, including poly propylene glycol, either in a compoundor neat. Lotions and skin care agents can be those described in co-ownedand co-pending U.S. Ser. No. 10/152,924, filed on May 21, 2002, U.S.Ser. Nos. 09/968,154, and 10/152,924, filed on May 21, 2002.

Interposed between the absorbent core 20 and topsheet 26 can be at leastone fluid permeable secondary topsheet 24. Secondary topsheet 24 can aidin rapid acquisition and/or distribution of fluid and is preferably influid communication with the absorbent core 20. In one embodiment, thesecondary topsheet 24 does not completely cover the absorbent core 20,but it can extend laterally to core periphery 30. In one embodiment,topsheet, secondary topsheet, or the absorbent core can be layeredstructures, the layers facilitating fluid transport by differences influid transport properties, such as capillary pressure.

Each web of absorbent core material can itself be a layered structurehaving discrete layers as is known in the art of air laying webs usingmultiple air laying heads or beams. In a layered absorbent corematerial, any one discrete layer can comprise a different type or blendof fibers with respect to one other discrete layer.

In one embodiment, absorbent core 20 does not extend laterally outwardto the same extent as either topsheet 26 or backsheet 22, but thesanitary napkin 10 outer periphery 28 can be substantially larger thanthe core outer periphery 30. In this manner, the region of sanitarynapkin 10 between the core periphery 30 and the sanitary napkin 10 outerperiphery 28 can define a breathable zone that permits vapors to gothrough portions of the sanitary napkin, thereby escaping and providingfor dryer comfort when worn. A sanitary napkin having a breathable zonecan be according to the teachings of U.S. Ser. No. 10/790,418, filedMar. 1, 2004.

All the components can be adhered together by means well known in theart with adhesives, including hot melt adhesives, as is known in theart. The adhesive can be Findlay H2128 UN or Savare PM 17 and can beapplied using a Dynafiber HTW system.

As is typical for sanitary napkins and the like, the sanitary napkin 10of the present invention can have panty fastening adhesive 18 disposedon the garment-facing side 17 of backsheet 22. Panty fastening adhesive18 can be any of known adhesives used in the art for this purpose, andcan be covered prior to use by a release paper 19, as is well known inthe art. If flaps or wings are present, panty fastening adhesive can beapplied to the garment facing side so as to contact and adhere to theunderside of the wearer's panties.

The above disclosure is meant to give a general description of the basicparts of feminine hygiene articles such as sanitary napkins and the likeas they are known in the art. The description is not intended to belimiting. Any and all of various known elements, features and processesof known sanitary napkins, pantiliners, sanitary napkins, and the likecan be incorporated in the feminine hygiene article of the presentinvention as desired or needed for commercial manufacture, or forparticular use benefits. For example, sanitary napkins can be accordingto the disclosure of U.S. Pat. No. 4,950,264 issued to Osborn III Aug.21, 1990, and an incontinence pad can be according to the disclosure ofU.S. Pat. No. 5,439,458 issued to Noel et al. Aug. 8, 1995.

The present invention utilizes absorbent materials that for sanitarynapkins can include a secondary topsheet and/or an absorbent core thathave been modified from an as-made state to exhibit higher permeabilitywithout a corresponding decrease in capillary pressure, such that thesecondary topsheet and/or core of the present invention provides forfaster acquisition rates and greater retained capacity relative to theunmodified material, and with respect to known materials. Thesedesirable properties can be imparted to known fibrous web materials byforming them by one or more of known formation means, such as by knownmethods for making extruded nonwoven webs and airlaid fibrous webs.Without being bound by theory, it is believed that the modificationsdisclosed herein produce modifications of the base web in the form ofrelatively small, localized, discrete regions of increased permeability,which together with the substantially unmodified regions, produce anaverage, or “macro” effect of a web in which the either the permeabilityor capillary pressure can be improved without the expected negativeimpact on the other.

In one aspect, known absorbent web materials in an as-made can beconsidered as being homogeneous throughout. Being homogeneous, the fluidhandling properties of the absorbent web material are not locationdependent, but are substantially uniform at any area of the web.Homogeneity can be characterized by density, basis weight, for example,such that the density or basis weight of any particular part of the webis substantially the same as an average density or basis weight for theweb. By the apparatus and method of the present invention, homogeneousfibrous absorbent web materials are modified such that they are nolonger homogeneous, but are heterogeneous, such that the fluid handlingproperties of the web material are location dependent. Therefore, forthe heterogeneous absorbent materials of the present invention, atdiscrete locations the density or basis weight of the web issubstantially different than the average density or basis weight for theweb. The heterogeneous nature of the absorbent web of the presentinvention permits the negative aspects of either of permeability orcapillarity pressure to be minimized by rendering discrete portionshighly permeable and other discrete portions to have high capillarity.Likewise, the tradeoff between permeability and capillarity pressure ismanaged such that delivering relatively higher permeability can beaccomplished without a decrease in capillarity pressure. Theheterogeneous web of the present invention appears to uncouple thepermeability/capillarity pressure tradeoff. The formation means and theabsorbent core materials made thereby are described below.

Four formation means known for deforming a generally planar fibrous webinto a three-dimensional structure are utilized in the present inventionto modify as-made absorbent materials into absorbent materials havingrelatively higher permeability without a significant correspondingdecrease in capillary pressure. Each of the four formation meansdisclosed herein are disclosed as comprising a pair of inter-meshingrolls, typically steel rolls having inter-engaging ridges or teeth andgrooves. However, it is contemplated that other means for achievingformation can be utilized, such as the deforming roller and cordarrangement disclosed in US 2005/0140057 published Jun. 30, 2005.Therefore, all disclosure of a pair of rolls herein is consideredequivalent to a roll and cord, and a claimed arrangement reciting twointer-meshing rolls is considered equivalent to an inter-meshing rolland cord where a cord functions as the ridges of a mating inter-engagingroll. In one embodiment, the pair of intermeshing rolls of the instantinvention can be considered as equivalent to a roll and an inter-meshingelement, wherein the inter-meshing element can be another roll, a cord,a plurality of cords, a belt, a pliable web, or straps. Likewise, whilethe disclosure of four formation means is illustrated herein, otherknown formation technologies, such as creping, necking/consolidation,corrugating, embossing, button break, hot pin punching, and the like arebelieved to be able to produce absorbent materials having some degree ofrelatively higher permeability without a significant correspondingdecrease in capillary pressure.

The first formation means useful in the present invention is a processcommonly referred to as “ring rolling”. Referring to the drawings, andparticularly to FIG. 2 thereof, there is schematically illustrated at 32apparatus and a method for modifying the physical and performanceproperties of a web by the process commonly referred to as ring rolling,for example, a nonwoven web 34 that is carried on and that is drawn froma supply roll 36. For absorbent core materials, such as air laidnonwoven webs, the ring rolling apparatus and method can produce aphysically modified web having improved fluid handling properties andmodified dimensions that may serve to improve both the performance andthe fit of disposable articles that incorporate such modified materials.Additionally, after being modified in the disclosed apparatus and afterhaving acquired the desired physical properties hereinafter described,such modified nonwoven webs are capable of further processing, ifdesired, whether alone or together with other materials, and without themodified nonwoven web experiencing disintegration, rupture, or loss ofintegrity.

Referring again to FIG. 2, nonwoven web 34 is withdrawn from supply roll36 and travels in the direction indicated by the arrow. Nonwoven web 34is fed to the nip 38 formed by a pair of opposed forming rolls 40 and 42that together define a first forming station 6 . The structure andrelative positions of forming rolls 40 and 42 of first forming station 6are shown in an enlarged perspective view in FIG. 3. As shown, rolls 40and 42 are carried on respective rotatable shafts 44, 46, having theiraxes of rotation disposed in parallel relationship. Each of rolls 40 and42 includes a plurality of axially-spaced, side-by-side,circumferentially-extending, equally-configured ridges 52 that can be inthe form of thin fins of substantially rectangular cross section, orthey can have a triangular or an inverted V-shape when viewed in crosssection. If they are triangular, the vertices of ridges 52 are outermostwith respect to the surface of rolls 40 and 42. In any configuration,the outermost tips of the teeth are preferably rounded, as shown ingreater detail in FIGS. 4 and 5, to avoid cuts or tears in thematerials, such as nonwoven web 34, that pass between the rolls.

The spaces between adjacent ridges 52 define recessed,circumferentially-extending, equally configured grooves 54. The grooves54 can be of substantially rectangular cross section when the teeth areof substantially rectangular cross section, and they can be of invertedtriangular cross section when the teeth are of triangular cross section.Thus, each of forming rolls 40 and 42 includes a plurality of spacedridges 52 and alternating grooves 54 between each pair of adjacentteeth. The teeth and the grooves need not each be of the same width,however, and preferably the grooves have a larger width than that of theteeth, to permit the material that passes between the interengaged rollsto be received within the respective grooves and to be locallystretched, as will be explained hereinafter.

FIG. 4 is an enlarged, fragmentary, cross-sectional view showing theinterengagement of ridges 52 and grooves 54 of the respective rolls.Ridges 52 have a ridge height RH and are spaced apart from one anotherby a preferably uniform distance to define a pitch P. As shown, ridges52 of one roll extend partially into grooves 54 of the opposed roll todefine a “depth of engagement”, DOE, as shown in FIG. 4. The respectiveaxes of rotation of rolls 40 and 42 are spaced from each other such thatthere is a predetermined space or gap between the opposed sidewalls ofthe interengaged teeth and grooves of the respective rolls.

FIG. 5 is an even further enlarged view of several interengaged ridges52 and grooves 54 with a web 34 of material therebetween. As shown, aportion of a web, which can be nonwoven web 34 as shown in FIG. 1, isreceived between the interengaged teeth and grooves of the respectiverolls. The interengagement of the teeth and grooves of the rolls causeslaterally spaced portions of web 34 to be pressed by ridges 52 intoopposed grooves 54. In the course of passing between the forming rolls,the forces of ridges 52 pressing web 34 into opposed grooves 54 imposewithin web 34 tensile stresses that act in the cross-web direction. Thetensile stresses can cause intermediate web sections 58 that lie betweenand that span the spaces between the tips of adjacent ridges 52 tostretch or extend in a cross-web direction, which can result in alocalized reduction of the web thickness at each of intermediate websections 58. For nonwoven webs, including airlaid webs, the stretchingcan cause fiber reorientation, a reduction in basis weight, and orcontrolled fiber destruction in the intermediate web sections 58.

Although the portions of web 34 that lie between the adjacent ridges arelocally stretched, the portions of the web that are in contact the tipsof the ridges may not undergo a similar degree of extension. Because ofthe frictional forces that exist between the surfaces at the roundedouter ends of ridges 52 and the adjacent areas 60 of web 34 that are incontact with the ridge surfaces at the outer ends of the ridges, slidingmovement of those portions of the web surfaces relative to the ridgesurfaces at the outer ends of the ridges is minimized. Consequently, insome cases, the properties of the web 34 at those areas of the web thatare in contact with the surfaces of the ridge tips changes onlyslightly, as compared with the web property changes that occur atintermediate web sections 58.

Because of the localized cross-web stretching of web 34 that has takenplace, with the consequent increase in web width, the web material thatexits from the forming rolls can have a lower basis weight than that ofthe entering web material, provided the exiting material remains in asubstantially flat, laterally extended state. The laterally-stretchedweb as it exits from between the forming rolls may contract laterally toits original width, in that the web is placed under some tension in theweb movement direction, in which case the exiting, modified web may havethe same basis weight as it had in its entering condition. If, however,the exiting web is subjected to a sufficiently high web machinedirection tension, the exiting web can be made to contract to a smallerwidth than its original width, in which case the web will have a greaterbasis weight than its original basis weight. On the other hand, if theweb is subjected to sufficient additional cross-web stretching bypassing the modified web between so-called Mount Hope rolls, tenteringframes, angled idlers, angles nips, or the like as described above, theexiting, modified web can have less than its original basis weight.Thus, by selecting a suitable forming roll tooth and grooveconfiguration, by selecting a suitable web movement direction tensionlevel, and by selecting whether or not to subject the web to additionalcross-web stretching, the resulting modified nonwoven web can have a webwidth that can range from about 25% to about 300% of the initial webwidth and a basis weight that is less than, equal to, or greater thanthe web's original basis weight.

Ridges 52 can be generally triangular in cross section having generallyrounded ridge tips, as shown in FIGS. 4 and 5, and preferably each ofridges 52 is of the same size so that each of the opposed ridges andgrooves on respective forming rolls 40 and 42 interengage with eachother along the entire axial lengths of each of the rolls. As shownridges 52 have a ridge height RH (note that RH can also be applied togroove depth; in one embodiment tooth height and groove depth can beequal), and a ridge-to-ridge spacing referred to as the pitch P. Thedepth of engagement DOE, ridge height RH, and pitch P can be varied asdesired depending on the properties of the nonwoven webs being processedand the desired characteristics of the processed webs. For example, ingeneral, the greater the depth of engagement DOE, the greater thenecessary elongation or fiber-to-fiber mobility characteristics thefibers of the processed web must possess.

By way of example, and not by way of limitation, ridges having apeak-to-peak pitch P of the order of about 0.150 inches, havingsidewalls disposed at an included angle of the order of about 12° andhaving a uniformly rounded ridge tip radius, and having a tip-to-baseridge height RH (and groove depth) of the order of about 0.300 inchescan be employed in carrying out the present invention. As will beappreciated by those skilled in the art, the sizes of the respectiveridges and grooves can be varied within a wide range and would still beeffective to carry out the present invention. In that regard, additionalstructural details of suitable forming rolls are provided in U.S. Pat.No. 5,156,793, entitled “Method for Incrementally Stretching Zero StrainStretch Laminate Sheet in a Non-Uniform Manner to Impart a VaryingDegree of Elasticity Thereto,” which issued on Oct. 20, 1992, to KennethB. Buell et al.; in U.S. Pat. No. 5,167,897 entitled “Method forIncrementally Stretching a Zero Strain Stretch Laminate Sheet to ImpartElasticity Thereto,” which issued on Dec. 1, 1992, to Gerald M. Sheeteret al.; and in U.S. Pat. No. 5,518,801, entitled “Sheet MaterialsExhibiting Elastic-Like Behavior,” which issued on May 21, 1996, toCharles W. Chappell et al.

The second means for deforming a web of the present invention is aprocess commonly referred to as a “SELF” or “SELF'ing” process, in whichSELF stands for Structural Elastic Like Film. While the process wasoriginally developed for deforming polymer film to have beneficialstructural characteristics, it has been found that the SELF'ing processcan be used to produce beneficial structures in nonwoven webs useful asabsorbent core materials, including air laid absorbent cores, asdisclosed herein.

Referring to FIG. 6, there is shown a configuration of opposed formingrolls for use in a SELF process that can be employed to expand portionsof a nonwoven web in the web thickness dimension, by expanding portionsof the web out of the X-Y plane in the Z-direction. As shown in FIG. 7,an unmodified nonwoven web 34 can be fed from a supply roll 36 into thenip 38 of opposed forming rolls 62 and 64. Roll 64 includes a pluralityof circumferentially-extending, axially-spaced circumferential ridges 52and grooves 54 similar to those described with respect to the rolls 40and 42 above. Roll 62 includes a plurality ofcircumferentially-extending, axially-spaced circumferential ridges 52wherein portions of the circumferential ridges 52 of roll 62 have beenremoved to form notches 66 that define a plurality ofcircumferentially-spaced teeth 68. As shown in FIG. 6, notches 66 onrespective axially adjacent circumferential ridges 52 can be alignedlaterally to define a plurality of circumferentially-spaced groups ofnotched regions about the periphery of roll 62. The respectivelaterally-extending groups of notched regions each extend parallel tothe axis of roll 62. Teeth 68 can have a tooth height TH correspondingto ridge height RH, as illustrated in FIG. 4, and a tooth pitchcorresponding to the ridge pitch P, as illustrated in FIG. 4.

As web 34 passes through nip 38, the teeth 68 of roll 62 press a portionof web 34 out of plane to cause permanent, localized Z-directiondeformation of web 34. But the portion of the web 34 that passes betweenthe notched regions 66 of roll 62 and the teeth 68 of roll 62 will besubstantially unformed in the Z-direction, i.e., the nonwoven web willnot be deformed or stretched in that area to the same degree as that ofthe toothed regions, and can remain substantially planar, while theportions of the web passing between toothed regions of roll 62 and theridges 52 of roll 64 can be deformed or stretched beyond the elasticlimit of the nonwoven, resulting in a plurality of deformed, raised,rib-like elements.

Referring now to FIG. 8, there is shown a schematic representation of aportion of a SELF'ed nonwoven web 70 after it has passed between a pairof opposed, interengaged forming rolls 62 and 64 of a SELF process, therolls having the tooth configurations similar to that shown in FIG. 6.SELF'ed nonwoven web 70 includes a network of distinct regions. Thenetwork includes at least a first region 72, a second region 74, and atransitional region 76, which is at the interface between the firstregion 72 and the second region 74. SELF'ed nonwoven web 70 also has afirst surface 78 and an oppositely-facing second surface 80. In theembodiment shown in FIG. 8, SELF'ed nonwoven web 70 includes a pluralityof substantially flat, spaced first regions 72 and a plurality ofalternating rib-like elements 84. In the preferred embodiment of FIG. 8,the first regions 72 and the second regions 74 are substantially linear,each extending continuously in a direction substantially parallel to thelongitudinal axis of the web.

In the embodiment shown in FIG. 8 first regions 72 are substantiallyplanar. That is, the material within first regions 72 is substantiallyflat and is in substantially the same condition after the modificationstep undergone by nonwoven web 60 by passage between interengaged rolls62 and 64 shown in FIG. 6 as it was in before the web 34 was passedbetween the forming rolls.

In an air laid absorbent core, it has been found that the rib-likeelements 84 can beneficially be adjacent to one another and can beseparated from each other by an unformed first region 72 which caninclude the valleys 86 separating adjacent rib-like elements 84.Unformed first region 72 can be areas that have substantially the samematerial properties as the homogeneous air laid absorbent core beforeSELF'ing, and can have a width of less than about 0.10 inches measuredperpendicular to the x-axis as shown in FIG. 8. The dimensions of therib-like elements can also be varied, if desired. The rib-like elementsprotruding in the Z-direction with respect to the plane of the web areraised portions that increase the bulk or caliper of the web, withoutnecessarily increasing the basis weight thereof. The raised portionsalso define a continuous network of channels in the unformed firstregions 72, which channels define a void region between the surface ofthe web and any adjacent webs when the web is combined into a layeredabsorbent core for a disposable absorbent product, for example. In oneembodiment, the continuous network of channels can define a void regionadjacent the topsheet. The void regions can serve to provide void volumein an absorbent core, such that the absorbent core has greaterpermeability, and can handle “gushes” of fluid more effectively. Aninterconnected continuous network of channels has channels running inboth the MD and the CD directions in the plane of the absorbent core.Channels can facilitate lateral “run off” of fluid such that fluid canmore effectively be distributed across the length and width of anabsorbent core as well.

In one embodiment, the nonwoven web processed by the SELF processdescribed herein can be a web having absorbency characteristics suitablefor use as an absorbent core in a disposable absorbent article. In oneembodiment, the web can be an airlaid web of fibers, includingcellulosic fibers, synthetic fibers, and blends and combinationsthereof. In one embodiment, the airlaid web can be a layered airlaidweb, formed of layers in which each layer can differ from an adjacentlayer in fiber type, density, basis weight, or combinations thereof. Inone embodiment an absorbent core material having rib-like elementsformed therein can be used in a layered relationship with a topsheet,wherein the rib-like elements are oriented toward, and are in acontacting relationship with, the topsheet. In one embodiment anabsorbent core material having rib-like elements formed therein can beused in a layered relationship with a secondary topsheet, wherein therib-like elements are oriented toward, and are in a contactingrelationship with, the secondary topsheet. A secondary topsheet can bewhat is commonly referred to as a distribution layer, which can be anabsorbent material having fluid handling properties suitable for rapidlydistributing fluid in a lateral direction. Alternatively, in anotherembodiment, the rib-like elements can be used in a layered relationshipwith a topsheet or secondary topsheet, wherein the rib-like elements areoriented away from, and are not in a contacting relationship with, thetopsheet or secondary topsheet.

In addition to the surface pattern illustrated in FIG. 8 in the form ofrib-like elements each having substantially equal lengths and arrangedin rows to define generally rectangular areas of deformation separatedby linear first regions 72, the desired formation of a nonwoven web can,if desired, be effected by other forming roll tooth and grooveconfigurations that can cause localized stretching and/or deformation ofthe nonwoven material. For example, as shown in FIG. 9, instead ofspaced rectangular arrays of rib-like elements the deformation patterncan be in the form of rib-like elements defining an array of spaced,diamond-shaped second regions 74 with intervening undeformed firstregions 72. Each such diamond-shaped second region 74 is defined byalternating rib-like elements 84 and intervening valleys 86. Examples ofmethods and apparatus for formation of such diamond-shaped elements aredisclosed in U.S. Pat. No. 5,650,214, entitled, “Sheet MaterialsExhibiting Elastic-Like Behavior and Soft, Cloth-Like Texture”, whichissued on Jul. 22, 1997, to Barry J. Anderson, et al., and U.S. Pat. No.6,383,431, entitled, “Method of Modifying a Nonwoven Fibrous Web For Useas a Component of a Disposable Absorbent Article,” which issued May 7,2002, to Dobrin, et al.

As shown in FIG. 10, the deformation pattern can also be in the form ofrib-like elements 84 that together define an array of spaced,circularly-shaped second regions 74. Each such circular element can bedefined by appropriately spaced, varying-length rib-like elements 84 andintervening valleys 86. Between respective circularly-shaped secondregions 74 are unformed intervening first regions 72. As will beapparent to those skilled in the art, other deformation patterns canalso be employed, if desired, such as those illustrated and described inU.S. Pat. No. 5,518,801.

The third means for deforming a web of the present invention is aprocess that can best be described as “micro-SELF”. Micro-SELF is aprocess that is similar in apparatus and method to that of the SELFprocess described with reference to FIGS. 6 and 7. The main differencebetween SELF and micro-SELF is the size and dimensions of the teeth 68on the toothed roll, i.e., the micro-SELF roll 82 in FIG. 11, whichcorresponds to roll 62 of FIG. 6. Referring to FIG. 11 there is shown aschematic side view representation of a micro-SELF roll 82 that can beone of the rolls forming a nip roll arrangement in a preferredconfiguration having one patterned roll, e.g., micro-SELF roll 82, andone non-patterned grooved roll (not shown) similar to that shown as roll64 in FIG. 6. However, in certain embodiments it may be preferable touse two micro-SELF roll 82 having either the same or differing patterns,in the same or different corresponding regions of the respective rolls.Such an apparatus can produce webs with deformations that, in nonwovenwebs, can be described as tufts or loops protruding from one or bothsides of the processed web. The tufts can be closely spaced, but atleast at their base can be spaced apart sufficiently to define voidregion between tufts that permits fluid flow between adjacent tufts. Theexisting between tufts can define a continuous network of channels. Inthe micro-SELF roll of FIG. 12, individual teeth 68 can have a toothlength TL of about 0.051 inch (about 1.27 mm) with a distance betweenteeth TD of about 0.062 inch (about 1.57 mm) and a pitch of about 0.060inch (about 1.52 mm) In one embodiment the circumference of roll 82 canbe such that there are 158 teeth 68 separated by 159 cuts between teeth68.

As shown in the partial perspective view of FIG. 12 and the enlargedpartial perspective view of FIG. 13, the teeth 68 of a micro-SELF roll82 have a specific geometry associated with the leading and trailingedges of teeth 68 that permit the teeth to essentially “punch” throughthe nonwoven web 34 as opposed to, in essence, deforming the web intobumps or ridges as shown in FIGS. 8-10. In some embodiments of anonwoven web 34 suitable for use in an absorbent core, the teeth 68 urgefibers out-of-plane and to form what can be described as “tufts” orloops of fibers. In one embodiment, the web is punctured, so to speak,by the teeth 68 pushing the fibers through to form tufts or loops.Therefore, unlike the “tent-like” rib-like elements of SELF webs whicheach have continuous side walls associated therewith, i.e., a continuous“transition zone,” the tufts or loops forced out-of-plane in amicro-SELF process can have a discontinuous structure associated withthe side wall portions of the Z-direction deformations. Additionally,when utilized for relatively high basis weight absorbent core materials,the “tufting” can be somewhat invisible as fibers are urged out of theplane in a Z-direction with respect to one of the web surfaces, theZ-direction deformation may be muted or non-existent in the other websurface. Further, when a laminate material is involved, the Z-directiondeformations of one web material may be pushed into and “hidden” by thesecond material of the laminate, such that the “tufting” is essentiallyinvisible to the naked eye.

As shown in FIGS. 12 and 13, each tooth 68 has a tooth tip 112, aleading edge LE and a trailing edge TE. The tooth tip 112 is elongatedand has a generally longitudinal orientation. It is believed that to gettufted, looped tufts in the processed web, the LE and TE should be verynearly orthogonal to the local peripheral surface 90 of roll 82. Aswell, the transition from the tip 112 and LE or TE should be a sharpangle, such as a right angle, having a sufficiently small radius ofcurvature such that teeth 68 push through web 34 (as shown in FIG. 14)at the LE and TE. Without being bound by theory, it is believed thathaving relatively sharply angled tip transitions between the tip 112 oftooth 68 and the LE and TE permits the teeth 68 to punch throughnonwoven webs “cleanly”, that is, locally and distinctly, so that oneside of the resulting web can be described as “tufted” or otherwise“deformed.”

The teeth 68 of a micro-SELF roll 82 can have a uniform circumferentiallength dimension TL measured generally from the leading edge LE to thetrailing edge TE at the tooth tip 112 of about 1.25 mm and are uniformlyspaced from one another circumferentially by a distance TD of about 1.5mm. For processing a web having a total basis weight in the range ofabout 30 to about 500 gsm, teeth 68 of roll 82 can have a length TLranging from about 0.5 mm to about 3 mm and a spacing TD from about 0.5mm to about 3 mm, a tooth height TH ranging from about 0.5 mm to about 5mm, and a pitch P between about 1 mm (0.040 inches) and about 6.4 mm(0.250 inches). Depth of engagement DOE can be from about 0.5 mm toabout 5 mm (up to a maximum equal to tooth height TH). Of course, DOE,P, TH, TD and TL can be varied independently of each other to achieve adesired size, spacing, and area density of web deformations.

The fourth means for deforming a web suitable for use as an absorbentmaterial is a process that can best be described as “rotary knifeaperturing” (RKA). In RKA, a process and apparatus usingcounter-rotating meshing nip rolls 92 similar to that described abovewith respect to SELF or micro-SELF rolls is utilized, as shown in FIG.14. As shown, the RKA process differs from SELF or micro-SELF in thatthe relatively flat, elongated teeth of a SELF or micro-SELF roll havebeen modified to be generally pointed at the distal end. Teeth 68 can besharpened to cut through as well as deform nonwoven web 34 to produce athree-dimensionally apertured web 94 as shown in FIG. 14. In otherrespects such as tooth height, tooth spacing, pitch, depth ofengagement, and other processing parameters, RKA and the RKA apparatuscan be the same as described above with respect to SELF or micro-SELF.

FIG. 15 shows a portion of one embodiment of an RKA toothed rollerhaving a plurality of teeth 68 useful for making an apertured web 94. Anenlarged view of the teeth 68 is shown in FIG. 16. As shown in FIGS. 15and 16, each tooth 68 has a base 111, a tooth tip 112, a leading edge LEand a trailing edge TE. The tooth tip 112 can be generally pointed,blunt pointed, or otherwise shaped so as to stretch and/or puncture theprecursor web 34. Teeth 68 can have generally flattened, blade-likeshape. Teeth 68 can have generally flattened distinct sides 114. Thatis, as opposed to round, pin-like shapes that are generally round incross section, teeth 68 can be elongated in one dimension, havinggenerally non-round, elongated cross-sectional configurations. Forexample, at their base, teeth 68 can have a tooth length TL and a toothwidth TW exhibiting a tooth aspect ratio AR of TL/TW of at least 2, orat least about 3, or at least about 5, or at least about 7, or at leastabout 10 or greater. In one embodiment, the aspect ratio AR ofcross-sectional dimensions remains substantially constant with toothheight.

In one embodiment of an RKA toothed roll, teeth 68 can have a uniformcircumferential length dimension TL of about 1.25 mm measured generallyfrom the leading edge LE to the trailing edge TE at the base 111 of thetooth 68, and a tooth width TW of about 0.3 mm which is the longestdimension measured generally perpendicularly to the circumferentiallength dimension at the base. Teeth can be uniformly spaced from oneanother circumferentially by a distance TD of about 1.5 mm. For making asoft, fibrous three-dimensional apertured web from a precursor webhaving a basis weight in the range of from about 5 gsm to about 500 gsm,teeth 68 can have a length TL ranging from about 0.5 mm to about 3 mm, atooth width TW of from about 0.3 mm to about 1 mm, and a spacing TD fromabout 0.5 mm to about 3 mm, a tooth height TH ranging from about 0.5 mmto about 10 mm, and a pitch P between about 1 mm (0.040 inches) and 2.54mm (0.100 inches). Depth of engagement DOE can be from about 0.5 mm toabout 5 mm (up to a maximum approaching the tooth height TH).

Of course, DOE, P, TH, TD and TL can each be varied independently ofeach other to achieve a desired size, spacing, and area density ofapertures (number of apertures per unit area of aperturedthree-dimensionally apertured). For example, to make apertured films andnonwovens suitable for use in sanitary napkins and other absorbentarticles, tooth length TL at the base can range between about 2.032 mmto about 3.81 mm; tooth width TW can range from about 0.508 mm to about1.27 mm; tooth spacing TD can range from about 1.0 mm to about 1.94 mm;pitch P can range from about 1.106 mm to about 2.54 mm; and tooth heightTH can be from about 2.032 mm to about 6.858 mm. Depth of engagement DOEcan be from about 0.5 mm to about 5 mm. The radius of curvature R of thetooth tip 112 can be from 0.001 mm to about 0.009 mm. Without beingbound by theory, it is believed that tooth length TL at the base canrange between about 0.254 mm to about 12.7 mm; tooth width TW can rangefrom about 0.254 mm to about 5.08 mm; tooth spacing TD can range fromabout 0.0 mm to about 25.4 mm (or more); pitch P can range from about1.106 mm to about 7.62 mm; tooth height TH can range from 0.254 mm toabout 18 mm; and depth of engagement DOE can range from 0.254 mm toabout 6.35 mm. For each of the ranges disclosed, it is disclosed hereinthat the dimensions can vary within the range in increments of 0.001 mmfrom the minimum dimension to the maximum dimension, such that thepresent disclosure is teaching the range limits and every dimension inbetween in 0.001 mm increments (except for radius of curvature R, inwhich increments are disclosed as varying in 0.0001 mm increments).

RKA teeth can have other shapes and profiles and the RKA process can beused to aperture fibrous webs, as disclosed in co-pending, commonlyowned patent applications US 2005/0064136A1, filed Aug. 6, 2004, US2006/0087053A1, filed Oct. 13, 2005, and US 2005/021753 filed Jun. 21,2005.

Each of the web deforming processes described above is known in the artfor processing various webs of an absorbent article. For example, ringrolling is known to be used in combination with a thermal melt weakeningstep to produce apertures, as disclosed in U.S. Pat. Nos. 5,628,097 and5,916,661, and US 2003/0028165A1. As well, the SELF process is wellknown for making stretch portions of a topsheet as disclosed in US2004/0127875A1, filed Dec. 18, 2002. Micro-SELF rolls are known toproduce beneficially-modified topsheets as disclosed in US2004/0131820A1, WO 2004/059061A1 and WO 2004/058118A1. And RKA is knownto produce apertured formed films, nonwoven webs, and laminates, asdisclosed in US 2005/021753. Absorbent cores have also been modified bymicro-SELF rolls as disclosed in WO 2004/058497A1 in which a laminate oftwo webs is made by processing two webs together to form afiber-integrated composite absorbent core.

In each of the processes described above heat can be utilized, either byheating the web before the nip of the rollers or by way of heatedrollers, or heating the web after leaving the nip rollers. If any of therollers of the apparatuses as described above are to be heated, caremust be taken to account for thermal expansion. In one embodiment, thedimensions of ridges, grooves, and/or teeth are machined to account forthermal expansion, such that the dimensions described herein can bedimensions at operating temperature.

In one embodiment, processing of an absorbent core material can beachieved by the method disclosed in commonly-owned, co-pending USApplication No. 2006/0286343A1 entitled Tufted Fibrous Web. This methodcan include a heating means in which the tips, or distal ends, of webfeatures such as ribs or tufts can be heated and/or bonded. Such heatingand/or bonding can increase the crush-resistance of an absorbent core,and can improve its resiliency, which is important for maintainingpermeability under pressure. Resiliency can be improved by incorporatingthermoplastic bonding powders, such as polyethylene powder into thefibrous web, and then heating in regions where bonding is desired.Resiliency can also be improved by application of coatings, such aslatex coatings, that can tend to stiffen fibers, for example.

In one embodiment, multiple absorbent core layers can be integrated byinter-entangling fibers from adjacent webs. Fiber entanglement ofadjacent layers can be achieved by the processes described herein, andalso by known means such as needle-punching, hydroentangling, andthermal point bonding. By the same processes and means, it may bedesirable to integrate the topsheet of an absorbent article with anunderlying layer, such as a secondary topsheet modified by the processesdisclosed herein.

While the various web deforming processes described above are known fortopsheets, backsheets, and composite absorbent cores, the novel featureof the present invention is the application of these processes toachieve unexpected fluid handling property results in absorbenthomogeneous webs processed individually to be heterogeneous, and thencombined in a layered relationship with other webs that can also havebeen processed by a web deforming process to be heterogeneous. Combinedwebs need not be affixed in a joined relationship, but can be joined ifdesired by means known in the art, such as by adhesive bonding, thermalbonding, fiber entangling, latex bonding, and combinations thereof. Theinvention is believed to be applicable to a wide variety of fibers,including bicomponent fibers, nano-fibers, shaped fibers, andcombinations thereof, as well as a wide variety of webs by variousforming processes, including meltblown, spunbond, and carded webs,wet-laid webs including tissue paper, or combinations of theseprocesses. The invention is described below in a specific embodiment ofairlaid absorbent fibrous webs, i.e., core materials made by air layingprocesses.

Air laying is a process for making nonwoven webs in which cut staplefibers are introduced into an air stream which forces the fibers onto alaydown belt in a controlled manner. The fibers may be natural orsynthetic, and may be bonded by thermal, chemical, or mechanical meansinto a consolidated nonwoven web. When fibers are supplied as cut,stable fibers in compacted form, the airlaid process begins with adefibration system to open and feed the staple fibers into an airstream. Other functions can also be carried out, such at the dosage andintroduction of super absorbents or other powders. The fibrous and/orother materials are suspended in air within a forming system andsubsequently deposited onto a moving forming screen or rotatingperforated cylinder to form a randomly oriented air formed batt. The airformed batt can be bonded by applying latex binder and drying, thermallybonding thermoplastic staple fibers in the web, hydrogen or embossedbonding or a combination of these consolidation techniques. Airlaid webformation is taught in U.S. Pat. No. 4,640,810, to Laursen et al.Airlaid webs can be made by air laying a blend of fibrous materials, orby air laying discrete layers, each layer having a different type orblend of fibers.

In general, known methods of making airlaid materials producehomogeneous webs of airlaid material. As used herein, “homogeneous”refers to the uniformity of the web in the MD-CD plane, as indicated inFIG. 14, for example. As shown in FIG. 14, prior to formation throughnip 38, web 34 can be formed by a typical airlaid process so that in theMD-CD plane the web is substantially uniform in bulk properties such asdensity and basis weight. Virtually any discrete region chosen in theMD-CD plane of a homogeneous web would have the same material handlingproperties as an immediately adjacent region. Note that homogeneous doesnot refer to the nature of the web in the “Z-direction,” i.e., in adirection perpendicular to the MD-CD plane, which can be considered asbeing the thickness of the web. Web properties can vary in theZ-direction by layering fibers in a non-uniform manner through thethickness of the web.

As used herein, “heterogeneous” refers to the non-uniformity of the webin the MD-CD plane, as indicated in FIG. 14, for example. As shown inFIG. 14, after formation through nip 38, web 34 has been renderedheterogeneous such that in the MD-CD plane the web is substantiallynon-uniform in bulk properties such as density and basis weight.Discrete regions of the web have been mechanically deformed into tufts,apertures, or other three-dimensionally formed structures, such thatdiscrete portions of the web in the MD-CD plane would have the verydifferent material handling properties compared to immediately adjacentregions.

The size of the discrete portions under consideration can vary dependingon the size of the web and the purpose of the heterogeneous web. Ingeneral, however, it is desirable to have closely spaced discreteportions on the order of from about 1 to about 30 per square centimeter,including every whole number in between, including from about 5 to about10 per square centimeter. By having relatively closely spaced (in theMD-CD plane) discrete portions in the form of ribs, tufts, or apertures,for example, fluid handling is improved by increasing the probabilitythat a given drop of fluid on the web can experience both highpermeability and high capillarity options upon contact with the web.

To illustrate the present invention, generally homogeneous absorbentairlaid fibrous web materials were modified by one or more of the fourprocesses described above to achieve a heterogeneous absorbent corematerial having the ability to advantageously move fluid rapidly intosecure storage in the absorbent core when used in a sanitary napkin. Inone aspect, the heterogeneity of the absorbent core permits the core toexhibit fluid moving properties generally laterally, that is, in theplane of the web material. That is, rather than exhibit heterogeneity inthe Z-direction, i.e., in a direction through the thickness of the web,the web of the present invention can exhibit heterogeneity in the “X-Y”plane, i.e., in a plane parallel with the plane of the web in generallyflattened condition, referred to herein as lateral fluid movement.

Tables 1 and 2 below illustrate the benefits of processing an airlaidfibrous absorbent material by one or more of the four formation meansdescribed above. For all dimensions 1 inch equals 25.4 mm.

Table 1 shows variations in fluid handling properties for a web referredto herein as Absorbent Core I, made from an unmodified precursor webdescribed in Table 1 as Control Absorbent I. The Control Absorbent I webis an airlaid absorbent core material having a basis weight of about 180grams per square meter (gsm) and comprising cellulosic fibers andbicomponent fibers blended in an air laying process together with 30 gsmof absorbent gelling material (AGM). The cellulosic fibers are WeycoNB416 obtained from Weyerhaeuser Co. The bicomponent fibers are Invista#35160A (PE/PET, 2.0 denier and 4 mm length) obtained from Invista andthe proportion of cellulosic fibers to bicomponent fibers is 5 gram to 1gram. The AGM is Degussa 23070G obtained from Degussa, and is dispersedsubstantially uniformly throughout the web. About 5 w t% latex AF 192obtained from Air Products is sprayed on the surface of both sides andallowed to cure.

Table 2 shows variations in fluid handling properties for a web referredto herein as Absorbent Core II, made from an unmodified precursor webdescribed in Table 1 as Control Absorbent II. The Control Absorbent IIis an airlaid absorbent material suitable for use as a secondarytopsheet and is a laminate having a basis weight of about 82 grams persquare meter (gsm). One layer of the laminate of Control Absorbent II isa spunbond polypropylene (PP) hydrophilic nonwoven having a basis weightof about 22 gsm. The spunbond web layer can be obtained as P9 fromFiberweb. The spunbond polypropylene web is laminated to a web producedin an air laying process, the air laid web being a 60 gsm web ofcellulosic fibers and polyethylene powder binder blended in the airlaying process. About 5 wt % latex AF 192 obtained from Air Product wassprayed on the surfaces of the air laid web prior to lamination to thespunbond material. The cellulosic fibers are Weyco NB416 obtained fromWeyerhaeuser Co. The polyethylene powder binder is Dow Low Densitypolyethylene 959s obtained from Dow, and the proportion of cellulosicfibers to polyethylene powder binder is 3 g to 1 g. After air laying,the laminate web is processed through a heating step to effect thebinding properties of the polyethylene binder powder.

As shown in Table 1, the absorption capillary pressure and desorptioncapillary pressure, the grams per gram capacity, the permeability, andthe flow rate can each be changed in a beneficially positive manner byformation by the denoted processes. Each of the parameters weredetermined by the tests shown in the Test Methods section below.

TABLE 1 Fluid Handling Properties of Modified Airlaid Fibrous AbsorbentCore I Absorption Desorption Capillary Capillary Flow Sample PotentialPotential Capacity Permeability Rate No. Formation Process Type (mJ/m²)(mJ/m²) (g/g) (Darcy's) (g/sec) 1 Control Absorbent I 636 1111 4.14 1715.65 2 SELF 707 1297 6.76 360 8.8 3 SELF 632 1257 6.04 271 7.66 4 RKA677 1167 5.03 240 6.96 5 SELF 732 1260 6.01 348 9.12 6 SELF 614 11726.15 399 11

Sample No. 2 was made by processing Control Absorbent I through aSELF'ing process with the toothed roll shown in FIGS. 17-20. In oneembodiment, as shown in FIGS. 19 and 20 the teeth had a pitch P of 0.100inches, a tooth height TH of about 6.86 mm (about 0.270 inches), and atooth angle TA between teeth of about 9.478 degrees. Each tooth had atooth length TL of about 5.33 mm (about 0.2101 inches), a tooth spacingTD of about 1.98 mm (about 0.0781 inches), and a diverging tooth angleDA of about 2.903 degrees. The mating roll was an un-toothed roll, thatis, a roll having circumferentially extending ridges and grooves,similar to that shown in FIG. 6 above, and engaged at a DOE of about1.78 mm (about 0.070 inch). The SELF'ing process was carried out at roomtemperature at a rate of about 1-5 m/min.

Sample No. 3 was made by processing Control Absorbent I through aSELF'ing process with the toothed roll shown in FIGS. 21-23. FIG. 21 isa flat-out view of the circumference of a toothed roll. One differencefrom the tooth configuration of the embodiment shown in FIGS. 21-23 andthe embodiment used to make Sample 2 is that the teeth, rather thanhaving a generally rectangular shape when viewed from the top (i.e., inplan view, looking down on the surface of the roll), each tooth has agenerally diamond shape as shown in FIG. 23. Also, the pitch P fromtooth to tooth in a row is 0.200 inch, which results in a 0.100 pitch Pfrom tooth to tooth in a stagger pattern. Teeth 68 have a tooth lengthTL of about 5 mm, and a tooth distance TD of about 4 mm. The mating rollwas an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above,wherein the two mating rolls meshed at a DOE of about 1.78 mm (about0.070 inch). The SELF'ing process was carried out at room temperature ata rate of about 1-5 m/min.

Sample No. 4 was made by processing Control Absorbent I through a RKAprocess with the toothed roll shown in FIGS. 24-27. In the embodimentshown in FIGS. 24-27, the teeth of the toothed RKA roll were configuredin a staggered pattern having a row to row pitch P of about 2.54 mm(about 0.100 inch). The teeth 68 have a tooth length (measured at thebase) TL of about 3.81 mm (about 0.150 inch) and a tooth distance TD ofabout 1.94 mm (about 0.076 inch). The teeth 68 have a tooth width at thebase of about 1.27 mm and a tooth height TH of about 6.858 mm (about0.270 inch). The mating roll was an un-toothed roll, that is, a rollhaving circumferentially extending ridges and grooves, similar to thatshown in FIG. 6 above, and engaged at a DOE of about 6.35 mm (about0.250 inch). The RKA process was carried out at room temperature at arate of about 1-5 m/min.

Sample 5 was made by processing Control Absorbent I through a SELF'ingprocess in which the toothed roll had a configuration shown in FIGS.28-30. The teeth 68, rather than being in straight rows across the widthof the roll, are placed in staggered groups of three teeth that make agenerally circular shape to form a pattern on a processed web similar tothat shown in FIG. 10. As shown in FIG. 30, teeth 68 have a tooth heightTH of about 3.6 mm (0.14.5 inches) and a pitch P of about 1.524 mm(about 0.060 inch). The toothed roll was engaged with a mating ring rollhaving fully circumferential ridges and grooves similar to that shown inFIG. 6 above, engaged at a DOE of about 1.9 mm (about 0.075 inch). TheSELF'ing process was carried out at room temperature at a rate of about1-5 m/min.

Sample 6 was made by processing Control Absorbent I through a modifiedSELF'ing process in which an upper toothed roll had the configurationdescribed for the toothed roll of Sample 5. However, the inter-meshing(inter-engaging) roll, rather than having fully circumferential ridgesand grooves similar to that shown in FIG. 6 above, was another toothedmicro-SELF'ing roll similar to that shown in FIGS. 11-13, with a pitchof about 1.52 mm (about 0.060 inch) to match the upper toothed roll. Therolls were operated at a DOE of about 1.65 mm (about 0.065 inch). Theprocess was carried out at room temperature at a rate of about 1-5m/min.

As can be seen in Table 1, in all cases the grams (of absorbed fluid)per gram (of absorbent material) capacity, the permeability and the flowrate, all increased significantly, as did the capillary pressure in mostcases. All these improvements are a result of simply processing a webmaterial through the nip of a pair of intermeshing (or inter-engaging)rollers as described above. Therefore, there is no new material contentor new composition that would increase costs associated with the muchbetter fluid acquisition properties.

TABLE 2 Fluid Handling Properties of Modified Airlaid Fibrous AbsorbentCore II Absorption Desorption Capillary Capillary Flow Sample PotentialPotential Capacity Permeability Rate No. Formation Process Type (mJ/m²)(mJ/m²) (g/g) (Darcy's) (g/sec) 7 Control Absorbent II 301 596 3.75 10615 8 Ring roll 321 683 5.39 201 22 9 SELF 323 738 10.43 327 13 10micro-SELF 342 724 8.59 204 18 11 micro-SELF 324 696 6.07 185 18 12 RKA323 496 6.71 204 24 13 RKA 343 649 6.39 174 19 14 RKA 316 644 6.8 175 2015 RKA 321 651 5.39 121 16 16 SELF 322 657 8.24 165 15 17 SELF 309 6708.54 246 21 18 SELF 295 672 7.39 186 17 19 1^(st) pass: Ring roll 361641 7.68 208 23 2^(nd) pass: RKA 20 1^(st) pass: μ-SELF 367 757 8.58 25220 2^(nd) pass: RKA 21 1^(st) pass: μ-SELF 340 742 8.16 254 20 2^(nd)pass: RKA

Sample No. 8 was made by processing Control Absorbent II through a ringrolling apparatus as described with reference to FIGS. 2 and 3. The ringrolls had a pitch of about 1.016 mm (about 0.040 inch) and were meshedat a DOE of about 1.016 mm (about 0.040 inch). The process was carriedout at room temperature.

Sample 9 was made by processing Control Absorbent II throughintermeshing SELF rollers as described for Sample 2 above, with a DOE ofabout 2.45 mm (about 0.100 inch). The spunbond PP side of ControlAbsorbent II faced the non-toothed roll of the apparatus. The processwas carried out at room temperature.

Sample 10 was made by processing Control Absorbent II throughintermeshing micro-SELF rollers having a pitch P of about 1.52 mm (about0.060 inch) as described with respect to FIG. 11, and with a DOE ofabout 1.9 mm (about 0.075 inch). The spunbond PP side of ControlAbsorbent II faced the non-toothed roll of the apparatus. The processwas carried out at room temperature.

Sample 11 was made by processing Control Absorbent II throughintermeshing micro-SELF rollers having a pitch of about 1.52 mm (about0.060 inch) as described with respect to FIG. 11, and with a DOE ofabout 3.43 mm (about 0.135 inch). The spunbond PP side of ControlAbsorbent II faced the toothed micro-SELF roll of the apparatus. Theprocess was carried out at a temperature of 300 degrees F.

Sample 12 was made by processing Control Absorbent II through an RKAprocess with the toothed roll shown in FIGS. 31-34. The spunbond PP sideof Control Absorbent II faced the RKA roll of the apparatus. The teethof the toothed RKA roll were configured in a staggered pattern having arow to row pitch of about 1.016 mm (about 0.040 inch). Both the toothheight TH and tooth length TL were each about 2.032 mm (about 0.080inch). Tooth distance TD was about 1.626 mm (about 0.64 inch) and thetooth width TW was about 0.510 mm (about 0.020 inch) Other dimensionswere as shown. The mating roll was an un-toothed roll, that is, a rollhaving circumferentially extending ridges and grooves, similar to thatshown in FIG. 6 above at a DOE of about 6.35 mm (about 0.250 inch). TheRKA process was carried out at a temperature of 250 degrees F. at a rateof about 1-5 m/min.

Sample 13 was made by processing Control Absorbent II through an RKAprocess with the toothed roll shown in FIGS. 35-38. The spunbond PP sideof Control Absorbent II faced the RKA roll of the apparatus. The teeth68 of the toothed RKA roll were configured in a staggered pattern havinga row to row pitch P of about 1.524 mm (about 0.060 inch). The toothheight TH was about 3.683 mm (about 0.145 inch), the tooth distance TDwas about 1 mm (about 0.039 inch), and the tooth length TL was about2.032 mm (about 0.080 inch). Other dimensions were as shown. The matingroll was an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above at aDOE of about 3.43 mm (about 0.135 inch). The RKA process was carried outat a temperature of 300 degrees F. at a rate of about 1-5 m/min.

Sample 14 was made by processing Control Absorbent II through an RKAprocess with the toothed roll shown in FIGS. 24-27, as described above.The spunbond PP side of Control Absorbent II faced the RKA roll of theapparatus. The mating roll was an un-toothed roll, that is, a rollhaving circumferentially extending ridges and grooves, similar to thatshown in FIG. 6 above at a DOE of about 6.35 mm (about 0.250 inch). TheRKA process was carried out at a temperature of 350 degrees F. at a rateof about 1-5 m/min.

Sample 15 was made by processing Control Absorbent II through an RKAprocess with the toothed roll shown in FIGS. 24-27 as described above.The spunbond PP side of Control Absorbent II faced the RKA roll of theapparatus. The mating roll was an un-toothed roll, that is, a rollhaving circumferentially extending ridges and grooves, similar to thatshown in FIG. 6 above at a DOE of about 6.35 mm (about 0.250 inch). TheRKA process was carried out at room temperature at a rate of about 1-5m/min.

Sample 16 was made by processing Control Absorbent II through a SELF'ingprocess in which the toothed roll had teeth having the dimensions asdescribed with respect to Sample 5 above. The spunbond PP side ofControl Absorbent II faced the SELF roll of the apparatus. The matingroll was an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above at aDOE of about 1.9 mm (about 0.075 inch). The process was carried out atroom temperature at a rate of about 1-5 m/min.

Sample 17 was made by processing Control Absorbent II through a SELF'ingprocess in which the toothed roll had teeth having the dimensions asdescribed with respect to Sample 5 above. The spunbond PP side ofControl Absorbent II faced the SELF roll of the apparatus. The matingroll was an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above at aDOE of about 1.9 mm (about 0.075 inch). The process was carried out at atemperature of 300 degrees F. at a rate of about 1-5 m/min.

Sample 18 was made by processing Control Absorbent II through a SELF'ingprocess in which the toothed roll had teeth having the dimensions asdescribed with respect to Sample 5 above. The spunbond PP side ofControl Absorbent II faced the SELF roll of the apparatus. The matingroll was an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above at aDOE of about 1.65 mm (about 0.065 inch). The process was carried out atroom temperature at a rate of about 1-5 m/min.

Sample 19 was made by processing Control Absorbent II through twoseparate inter-engaging rollers. First, Control Absorbent II wasprocessed at room temperature through the nip of a ring roller having apitch of about 1.016 mm (about 0.040 inch), and a DOE of about 1.016 mm(about 0.040 inch). Next, the ring rolled web was processed through anRKA process with the toothed roll shown in FIGS. 31-34. The mating rollwas an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above at aDOE of about 1.143 mm (about 0.045 inch). The RKA process was carriedout at a temperature of 220 degrees F. at a rate of about 1-5 m/min.

Sample 20 was made by processing Control Absorbent II through twoseparate inter-engaging rollers. First, Control Absorbent II wasprocessed at room temperature through the nip of a micro-SELF rollerhaving a pitch of about 1.524 mm (about 0.060 inch), a DOE of about 1.9mm (about 0.075 inch), and at room temperature. The spunbond PP side ofControl Absorbent II faced the ring roll (non-toothed roll) of theapparatus. Next, the micro-SELF'ed web was processed through an RKAprocess with the toothed roll shown in FIGS. 31-34. The spunbond PP sideof Control Absorbent II faced the RKA roll of the apparatus. The matingroll was an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above at aDOE of about 2.16 mm (about 0.085 inch). The RKA process was carried outat a temperature of 300 degrees F. at a rate of about 1-5 m/min.

Sample 21 was made by processing Control Absorbent II through twoseparate inter-engaging rollers. First, Control Absorbent II wasprocessed at room temperature through the nip of a micro-SELF rollerhaving a pitch P of about 1.52 mm (about 0.060 inch), a DOE of about 1.9mm (about 0.075 inch), and at room temperature. The spunbond PP side ofControl Absorbent II faced the ring roll (non-toothed roll) of theapparatus. Next, the micro-SELF'ed web was processed through an RKAprocess with the toothed roll shown in FIGS. 24-27. The spunbond PP sideof Control Absorbent II faced the RKA roll of the apparatus. The matingroll was an un-toothed roll, that is, a roll having circumferentiallyextending ridges and grooves, similar to that shown in FIG. 6 above at aDOE of about 2.54 mm (about 0.100 inch). The RKA process was carried outat a temperature of 300 degrees F. at a rate of about 1-5 m/min.

As can be seen in Table 2, in almost all cases the capacity efficiencyin grams (of absorbed fluid) per gram (of absorbent material) capacity,the permeability and the flow rate, all increased significantly, as didthe capillary pressure in most cases. All these improvements are aresult of simply processing a web material through the nip of a pair ofinter-engaging rollers as described above. Therefore, there is no newmaterial content or new composition that would increase costs associatedwith the much better fluid acquisition properties.

As shown above in Tables 1 and 2, processing the airlaid webs by the webdeforming methods shown can have an immediate beneficial effect on thefluid handling properties of the web material. Without being bound bytheory it is believed that this beneficial effect is due to thedisruption of fibers in closely spaced discrete locations that producesdiscrete, but relatively closely spaced, regions of high or lowpermeability (depending on the specific web deformation process)surrounded by regions of low or high permeability, respectively. Forexample, in the example of ring rolling, the nature of the process is toproduce rows of high density, high capillarity material, separated byrows of low density, low capillarity materials. While it is recognizedthat ring rolling is well known in the art, it is believed that theapplication of ring rolling to air laid materials is a new applicationproviding for new and beneficial results in the art of absorbent corematerials.

In addition to the benefits observed when individual webs are processedas shown in Tables 1 and 2, additional surprising and unexpectedbenefits can be achieved when webs processed by one or more of the webdeforming processes described above are combined with other webs soprocessed, or processed by different web deforming processes. Thepresent invention is particularly valuable in the context of sanitarynapkins when one of the processed webs is used as a secondary topsheetand one of the webs is used as an absorbent core. The nomenclature“secondary topsheet” and “absorbent core” is not to be limiting. Thatis, the secondary topsheet can be considered to be an absorbent corealso, but the term is used herein in its normal sense as developed inthe art of sanitary napkins as a material used under and adjacent to atopsheet and having properties to move fluid away from the topsheet andinto the absorbent core. That is, while a secondary topsheet can haveabsorbent properties, it is not intended to keep fluid retained but isintended to give up fluid to an absorbent storage medium, e.g., anabsorbent core material, which absorbent core material is intended toretain fluid securely to ensure fluid does not return to the skin of thewearer.

The beneficial properties of the present invention can be illustratedwith reference to Table 3. In Table 3 is shown fluid handling propertiesof a variety of combinations of web materials from Tables 1 and 2, i.e.,the web materials having been deformed by one or more of the processesdescribed above. In Table 3, each combination of web materials fromTables 1 and 2 was tested in a configuration to model a sanitary napkin,and each sample was tested with an apertured formed film web of the typedisclosed in U.S. Pat. No. 4,629,643 issued to Curro et al. Dec. 16,1986 and as marketed by The Procter & Gamble Co. on its line of Always®brand sanitary napkins.

Therefore, for each Sample in Table 3, the structure tested was alayered structure comprising, in order, an apertured formed filmtopsheet, secondary topsheet (STS) of Core II, and an absorbent core ofCore I. Table 3 designates the particular air laid fibrous structures byreference to their respective sample numbers in Tables 1 and 2 above.

TABLE 3 Fluid Handling Properties of Combined Modified Airlaid FibrousAbsorbent Cores I and II Free HGW Sam- Gush Rewet Retained ple Run-offAcquisition Pressure Capacity No. Core I/Core II (%) (ml/sec) (psi) (g)22 Sample 7/sample 1 47 0.06 0.86 25 23 Sample 12/sample 1 39 0.07 1.6226 24 Sample 12/sample 2 34 0.10 1.61 26 25 Sample 13/sample 2 40 0.191.36 30 26 Sample 14/sample 2 35 0.11 1.19 28 27 Sample 10/sample 1 370.09 1.07 29 28 Sample 10/sample 2 28 0.13 0.87 29 29 Sample 21/sample 238 0.11 0.82 27 30 Sample 8/sample 1 52 0.07 1.00 26 31 Sample 8/sample2 37 0.12 0.96 26 32 Sample 19/sample 1 40 0.06 1.10 26 33 Sample19/sample 2 35 0.08 0.88 27

As shown in Table 3, the 2-layer absorbent cores of the presentinvention (as shown in Samples 23-33) can break the permeability versuscapillarity pressure tradeoff, by delivering relatively higherpermeability (as shown by Free Gush Run-off, Acquisition speed, andRetained Capacity) without a significant decrease in capillary pressure(as shown by Rewet Pressure) compared to the Control (Sample 22).

The web of the present invention, used as an absorbent core in anabsorbent product, exhibits properties that appear to have uncoupled thepermeability versus capillarity pressure tradeoff. Without being boundby theory, it is believed that this apparent uncoupling is due to thecreation of structures that have the effect of providing fluid handlingproperties in both of the tradeoff areas. For example, it is believedthat the processes disclosed produce discrete locations of greater voidvolume, which, particularly in multiple layer cores permits the corematerials to exhibit desirable benefits of both properties. The greatervoid volume in a fibrous material can result in greater permeability.These regions of greater permeability are relatively closely spaced,separated by the unmodified regions of the web, such regions exhibitingrelatively lower permeability but relatively high capillary pressure.Thus, fluid impinging on the core, such as menses absorbed through atopsheet of an absorbent article during use, is presented with thepossibility of both fluid dynamics, high permeability and highcapillarity pressure. In effect, the fluid dynamics of such cores can bethe result of taking advantage of the best of both material properties.

The material properties of the core of the present invention, whethersingle core or multiple core, can be further enhanced by additional corelayers, or additional layers of material in a given core material. Thatis, for example, additional airlaid webs can be modified by the methodsdisclosed herein and added in layered relationship with the other two ormore. As well, any one of the airlaid webs can itself be a layeredstructure exhibiting therein a Z-direction gradient in fluid handlingproperties. For example, for any one of the absorbent cores disclosedherein, including airlaid webs, the core can exhibit a Z-directiondensity gradient from low density on one side of the web to relativelyhigh density on the other. Likewise, permeability, capillarity, fibertype and size, and other physical properties can be varied in variouscombinations within a layered web, such that a Z-direction gradient ofvirtually any physical property of the web can be envisioned as beinguseful in the present invention.

In one embodiment of a layered absorbent core, such as a layered airlaidweb, it is contemplated that one layer could be designed to fractureupon treatment by the processes described herein, while other layer(s)do not. For example, a middle layer of a three layer airlaid web couldcomprise a material, such as a fibrous material, which fractures at lowlevels of strain, such that upon application of stress by the methodsdescribed herein, the middle layer fractures to form discrete, spacedapart apertures, while the remaining layers do not. In like manner alayer of a multi-layer web could be rendered into strips.

In one embodiment of a layered absorbent core, it is contemplated that alaminate could be formed in which one or more of the layers is anon-fibrous material, such as a foam or film web. For example, anabsorbent core of the present invention can comprise, or be combinedwith, an absorbent foam material, such as high internal phase emulsions(HIPE) foams.

In one embodiment, the pattern of modification, such as by teeth on aSELF roll, can be varied across the width of the web being modified. Forexample, the rolls of a SELF process can be designed such that the pitchP of the teeth and grooves varies across the width of the rolls, and,consequently, across the width of the web. In this manner, for example,an absorbent core can be produced in which the central regioncorresponding to the longitudinal centerline region of an absorbentarticle, can have a pattern of ridges, tufts, apertures, or otherfeature, that is different from either or both side regions.

A schematic representation of two cores of the present invention for thepurpose of illustrating density variation is shown in FIGS. 39 and 40.FIG. 39 shows a schematic representation of Sample 2 as detailed abovewith respect to Table 1. FIG. 40 shows a schematic representation ofSample 10 as detailed above with respect to Table 2. For both schematicrepresentations, the out of plane, localized Z-direction deformations ofthe base web are indicated as rectangles. The rectangles shown areapproximate representations of the relative X-Y boundaries of theZ-direction deformations, where X and Y can correspond to thecross-direction (CD) and machine-direction (MD), respectively. Therectangles show approximate representations of the “tent-like” rib-likeelements of Sample 2, and the tufts of Sample 10, each of which can havea distinct aspect ratio of length divided by width, the aspect ratio ofat least about 1.5 to 1, or 1.7 to 1, or 2.0 to 1 or 2.7 to 1, or 3 to1, or 5 to 1, or 10 to 1, and including all numerical values between 1.5and 10 in increments of one-tenth. The dimensions and shape ofrectangles as well as the spacing of adjacent rectangles can be producedusing visual imaging techniques, as is known in the art.

As shown in FIG. 39, rib-like elements indicated as “a” can be about 5.5mm long and about 2 mm wide. Each element can be separated from adjacentelements in the CD by a region indicated as “b” which can be about 0.6mm. Each element can be separated from adjacent elements in the MD by aregion indicated as “c” which can be about 1.3 mm. Density measurementsof the various regions “a”, “b”, and “c” show that SELF'ing of anonwoven web, such as a fibrous airlaid web, can make relatively lowdensity out-of-plane deformations. In the embodiment depicted in FIG.39, the base material had a density of about 0.221 g/cc, region “a” hada density of about 0.128 g/cc, region “b” had a density of about 0.199g/cc, and region “c” had a density of about 0.226 g/cc.

As shown in FIG. 40, tuft elements indicated as “a” can be about 1.7 mmlong and about 1 mm wide. Each tuft element can be separated fromadjacent elements in the CD by a region indicated as “b” which can beabout 0.6 mm. Each element can be separated from adjacent elements inthe MD by a region indicated as “c” which can be about 1.2 mm. Densitymeasurements of the various regions “a”, “b”, and “c” show thatmicro-SELF'ing of a nonwoven web, such as a fibrous airlaid web, canmake low density out-of-plane deformations. In the embodiment depictedin FIG. 40, the base material had a density of about 0.088 g/cc, region“a” had a density of about 0.0.072 g/cc, region “b” had a density ofabout 0.0.093 g/cc, and region “c” had a density of about 0.0.101 g/cc.

It is understood that the density values described above with respect toSamples 2 and 10 shown in FIGS. 39 and 40 are approximate, and thedensity values can vary depending on the base material properties, theprocess used to make Z-direction deformations, and other material andprocess variables. In general, it is believed that for airlaid webshaving at least a portion of fibers being cellulosic fibers, that adensity difference between the density of the base web and the densityof the Z-direction deformation of at least about 18% to about 50% isbeneficial for the present invention. The density difference between thedensity of the base web and the density of the Z-direction deformationcan be 20%, 30%, 40% or greater than 50%. The density difference isbelieved to be most beneficial when the density of the Z-directiondeformation is less than the density of the base material. The densityof the base material can be considered to be essentially the same as thedensity of region “c” in FIGS. 39 and 40 in a web processed by themethods of the present invention.

It is understood that the density values provided herein are values foruncompressed webs processed to make absorbent cores as described herein.The absorbent cores described herein may be used in folded, compressed,packaged, and/or stored disposable absorbent articles. Therefore, theas-used density differences may be different than the as-made densitydifferences. Therefore, it is believed that an absorbent core materialused in a packaged disposable absorbent article can exhibit a densitydifference between the density of the regions between Z-directiondeformations (e.g., the regions noted as “b” and “c” in FIGS. 39 and 40)and the density of the Z-direction deformation can be 5%, 10%, 20%, 30%,or greater than 40%. Currently it is believed that an airlaid nonwovenabsorbent core comprising cellulosic fibers is most beneficial when thedensity differences above are due to the density of the Z-directiondeformations being relatively lower than the density of the regionsbetween Z-direction deformations.

The density data as discussed above with respect to Samples 2 and 10shown in FIGS. 39 and 40 were obtained by using a MicroCT40 (ScancoMedical, Bassersdorf, Switzerland) x-ray scanner at high resolution, 35KeV energy, 300 micron integration time and 10 averaging. A field ofview of 20×20 mm in X/Y and 2-3 mm in Z (depending on the sample) withan x/y/z resolution of 10 microns in all directions was used for thetomographic reconstruction of the datasets. Each dataset wasapproximately 2048×2048 in x/y and around 200-300 slices in the zdirection. After removing the sample holder from the field of view, theremaining stack of slices was analyzed as follows:

1) A threshold of 1000 was used to distinguish between a fiber andbackground.

2) The Thickness at each x/y point was determined by finding the firstfiber (any pixel >1000) along the Z direction (perpendicular to the wipesurface) and the last fiber along the Z direction. The differencebetween these two Z values provided the thickness at each location inX/Y. This image was saved in TIFF format.

3) The Basis Weight image at each x/y point was determined by summingall the values >1000 along the Z direction. This image was saved in TIFFformat.

4) The Density image at each x/y point was determined to be the value ofthe basis weight image at (X,Y) divided by the value of the thicknessimage at (X,Y). Images of 0 thickness were set to 0 in the Densityimage. This image was saved in TIFF format.

5) The user then selects regions within the thickness image. Each regionis labeled either thick or thin. The thickness mean and standarddeviation, basis weight mean and standard deviation, and density meanand standard deviation are then calculated for the region chosen (ineach respective image) and reported out as desired, for example to a.csv file to an Excel® spreadsheet.

Test Methods

1. Artificial Menstrual Fluid Preparation

For each of the tests using Artificial Menstrual Fluid (AMF), prepare asfollows:

-   Step 1: Dilute 10 ml of reagent grade 85-95% w/w lactic acid to 100    ml with distilled water. Label as 10% v/v lactic acid.-   Step 2: Add 11.76 g of reagent grade 85% w/w potassium hydroxide    (KOH) to a flask and dilute to 100 ml with distilled water. Mix    until completely dissolved. Label as 10% w/v KOH.-   Step 3: Add 8.5 g sodium chloride and 1.38 g of hydrous monobasic    sodium phosphate to a flask and dilute to 1000 ml with distilled    water. Mix until completely dissolved. Label as monobasic sodium    phosphate solution.-   Step 4: Add 8.5 g sodium chloride and 1.42 g anhydrous dibasic    sodium phosphate to a flask and dilute to 1000 ml with distilled    water. Mix until completely dissolved. Label as dibasic sodium    phosphate solution.-   Step 5: Add 450 ml of dibasic phosphate solution to a 1000 ml beaker    and add monobasic sodium phosphate solution until the PH is lowered    to 7.2±0.1. Label as phosphate solution.-   Step 6: Mix 460 ml of phosphate solution and 7.5 ml of 10% KOH in a    1000 ml beaker. Heat Solution to 45° C.,±5° C. and then add 28    sterilized gastric mucin (ICN Biomedical Inc., Cleveland, Ohio).    Continue heating for 2.5 hours to completely dissolve the gastric    mucin. Allow the solution to cool to less than 40° C. and then add    1.8±0.2 ml of 10% v/v lactic acid solution. Autoclave the mixture at    121° C. for 15 minutes, then allow to cool to room temperature.    Mucous mixture should be used within 7 days. Label as gastric mucin    solution.-   Step 7: Mix 500 ml of gastric mucin solution and 500 ml of fresh,    sterile defibrinated sheep blood (Cleveland Scientific, American    Biomedical, Bath, Ohio) in a beaker. Label as artificial menstrual    fluid. Store refrigerated and use within 7 days.    2. Absorption Capillary Potential and Desorption Capillary Potential

Absorption Capillary Potential, also referred to as absorption energy,and Desorption Capillary Potential, also referred to as desorptionenergy, can be determined by evaluating capillary work potential foreach tested material.

The ability of absorbent materials to absorb or desorb fluid viacapillary potential is measure by the Capillary Work Potential.

-   Step 1: A TRI Autoporosimeter from TRI, Princeton, N.J., is used to    measure percentage of fluid saturation as a function of pressure of    the absorbent core I and II samples listed in table 1 and 2.-   Step 2: The testing fluid used here is n-hexadecane.-   Step 3: There are three testing cycles to generate three capillary    pressure vs. percent saturation curves:

1) 1st Absorption with dry material (imbibition)

2) Draining

3) 2nd Absorption with wet material

-   Step 4: The Absorption Capillary Potential (absorption Capillary    Work Potential (CWP)) is calculated by the integration of the 1st    absorption curve of capillary potential as a function of uptake    volume.    W=∫P _(cap(CV)) dCV (mJ/m²)

Where CV is the measured cumulative uptake volume (convertible tosaturation)

-   Step 5: The Desorption Capillary Pressure (desorption Capillary Work    Potential (CWP)) is calculated by the integration of the draining    curve of capillary pressure as a function of uptake volume.    W=∫P _(cap(CV)) dCV (mJ/m²)

Where CV is the measured cumulative uptake volume (convertible tosaturation)

3. Permeability (Darcy's) and Flow Rate (g/sec)

Permeability is determined from the mass flow rate of any given fluidthrough a porous medium. The procedure for determining both is asfollows:

-   Step 1: A through plane permeability device is used to automatically    dispense and measure flow of liquid through a sample by monitoring    the distance a column of water drops in relation to time and    pressure measure.-   Step 2: The pressure drop determines the mass flow rate of a fluid    through a porous medium across the sample.-   Step 3 (for flow rate of Table 1): The flow rate is determined at a    variable pressure in the falling hydro head mode using a salt    solution containing 2.75% Calcium Chloride as the fluid for all of    the Absorbent I samples in Table 1.-   Step 3 (for flow rate of Table 2): The flow rate is determined at    constant pressure using the constant hydro head mode using    distilled/de-ionized water as the fluid for all of the Absorbent II    samples in Table 2.-   Step 4: Darcy permeability and Flow Rate is calculated by the    equations below:    F=k(A/μ) (Δp/l)   (1)    K=9.87×10⁻¹³ k   (2)

Where: F =flow Rate (g/s)

-   -   k=permeability of the porous material (m²)    -   A=Cross sectional area available for flow (m²)    -   l=Thickness of the material (m)    -   μ=Fluid viscosity (cP)    -   Δp=Pressure Drop (cm H₂O)    -   K=permeability (Darcy's)        4. Free Gush Run-off (%)

This test measures the weight percentage of fluid not being acquired (%run-off) by an absorbent pad. The protocol includes loading 10 ml ofartificial menstrual fluid (AMF) on an unloaded (fresh) sanitary napkinwhich is placed at 15° incline angle in the CD direction (i.e., thewidth of a sanitary napkin in a flat condition). Reported values are theaverage of N=3.

AMF Preparation:

-   Condition AMF at 73±4° F. (23±2° C.) for 2 hours before drawing    fluid for testing.    Sample Preparation and Apparatus:-   Step 1: Pre-stress each pad to be tested by: holding the ends of the    pad and twisting it 10 times followed by folding the pad    approximately 90 degrees to make the ends meet 10 times.-   Step 2: Allow samples to be equilibrated for at least two hours in a    room conditioned to 73±4° F. (23±2° C.) temperature and 50±4%    relative humidity prior to testing.-   Step 3: Mark the center point at the narrowest width of the pad as    the target fluid loading point.-   The apparatus includes a sample holder ring stand with 15° fixed    incline base, a fluid delivery separatory funnel with a nozzle, and    a run-off basin.    Procedures:-   Step 1: Weigh each sample pad to be tested.-   Step 2: Place the pad onto the sample holder in the CD direction    with 15° incline angle and adjust the fluid delivery nozzle to be    centered over the marked center point and 0.5 inches (12.7 mm) above    the pad surface.-   Step 3: Fill 10 ml of AMF into the separatory funnel.-   Step 4: Quickly open the valve of the funnel and allow the 10 ml    fluid drained completely from the funnel onto the pad surface in 3    seconds or less.-   Step 5: Weigh the wet pad-   Step 6: Subtract the pad's dry weight from the wet weight to    determine the amount of fluid absorbed. Subtract this number from 10    to get the amount of fluid not absorbed (run-off). Then divide the    run-off amount by 10 and multiply the result times 100 to report as    the 10 ml Free Gush Run-Off.    5. HGW Retained Capacity

HGW is an absorbency test that measures the uptake of fluid by anabsorbent pad as a function of time.

AMF Preparation:

Condition AMF at 73±4° F. (23±2° C.) for 2 hours before drawing fluidfor testing.

Sample Preparation and Apparatus:

Allow sample pads to be equilibrated for at least two hours in a roomconditioned to 73±4° F. (23±2° C.) temperature and 50±4% relativehumidity prior to testing.

Procedure:

-   Step 1: Place the sample pad upside (top sheet side) down    horizontally in a holder basket suspended from an electronic    balance. Supply desired confining air pressure for either 0.06 psi    or 0.25 psi to the sample holder basket.-   Step 2: A fluid loading column's tube, containing AMF and connected    to a fluid reservoir at zero hydrostatic head relative to the pad,    is allowed to contact the topsheet of the pad as a point source and    the increase in weight of the sample is used as a fluid uptake    versus time.-   Step 3: The test proceeds until the pad is fully saturated.-   Step 4: 7-piles of filter paper are placed over the saturated pad    and a load of 0.25 psi (17.6 g/cm2), followed by 1.0 psi (70.3    g/cm2) is applied to squeeze-out the fluid.-   Step 5: HGW Retained Capacity is the weight in grams of fluid    remaining in the sample post squeeze-out.-   Reported values are the average of N=3.    6. Rewet Pressure

Rewet Pressure is the amount of pressure needed to cause liquid toemerge back through a previously wetted topsheet from a wet underlyingabsorbent core.

AMF Preparation:

Condition AMF at 73±4° F. (23±2° C.) for 2 hours before drawing fluidfor testing.

Sample Preparation and Apparatus:

-   Step 1: Allow sample pads to be tested to equilibrate for at least    two hours in a room conditioned to 73±4° F. (23±2° C.) temperature    and 50±4% relative humidity prior to testing.-   Step 2: The apparatus used to measure the loading force is a Tensile    Tester with light duty jaws such as EME model 607, model 627, or    model 599A, available from the EME Co., Newbury, Ohio. It is    equipped with a sample holder base plate and a compression sensor    foot which are also available form EME.    Procedure:-   Step 1: Place the sample pad topsheet side up and place a Plexiglas    fluid loading strike through cap, with a center hole, on the center    of the pad.-   Step 2: Dispense 7.5±0.3 ml of AMF through the center hole of the    strike through cap in 5 second or less.-   Step 3: As soon as the pad completely absorbs the fluid, remove the    strike through cap, then start the time for 5 minute.-   Step 4: Place the loaded sample pad onto the sample holder base    plate and center the compression sensor foot directly above the    stain area.-   Step 5: At the end of the 5 minute, start the tensile tester. The    cross head should move down to compression the sample until the    fluid is detected.-   Step 6: The rewet pressure is the compression force divided by the    area of the compression sensor foot.-   Reported values are the average of N=3.    7. Acquisition Rate (ml/sec)

This test measures gush acquisition rate, i.e., how fast the absorbentpad acquires fluid.

AMF Preparation:

Condition AMF at 73±4° F. (23±2° C.) for 2 hours before drawing fluidfor testing.

Sample Preparation:

Allow test pad samples to be equilibrated for at least two hours in aroom conditioned to 73±4° F. (23±2° C.) temperature and 50±4% relativehumidity prior to testing.

Procedures:

-   Step 1: Place a 4 inch square block with a 1 inch by 0.6 inch    opening (generally oval in shape) over the center of the sample pad    to be tested. Add sufficient weight to the block to achieve a 0.25    psi pressure, without obstructing opening.-   Step 2: Add AMF through the top of the opening to the sample pad at    a rate of 2 ml/hr for 2.25 hour via a Low Flow Syringe Pump from    Harvard Apparatus, Southnatick, Mass..-   Step 3: Then, add 3 ml AMF at once through the opening to the sample    pad using a Eppendorf Maxipipetter from Fisher Scientific. Time the    interval between the first drop of 3 ml AMF and no AMF is visible on    the top surface of the sample.-   Step 4: Calculate the Acquisition rate in ml/sec by dividing the    amount (3 ml) by the time in seconds measured in Step 3.-   Reported values are the average of N=3.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A sanitary napkin comprising a topsheet joined toa backsheet and having an absorbent core disposed therebetween, saidabsorbent core being a fibrous absorbent material exhibiting on one sidethereof a plurality of discrete raised portions, said discrete raisedportions defining a continuous network of channels, said channelsdefining a void region adjacent said topsheet of said sanitary napkin;wherein the plurality of discrete raised portions and the continuousnetwork of channels defines intermediate areas of localized reductionsin web thickness, the intermediate areas having a substantiallydifferent density or basis weight than the plurality of discrete raisedportions or the continuous network of channels and wherein the pluralityof discrete raised portions are rib-like elements; said discrete raisedportions defining an array of spaced, diamond-shaped regions or an arrayof spaced, circularly-shaped regions; and wherein one of the discreteraised regions has a density of about 0.128 g/cc, and at least onechannel has a density of about 0.199 g/cc.
 2. A sanitary napkincomprising a topsheet joined to a backsheet and having an absorbent coredisposed therebetween, said absorbent core being a fibrous absorbentmaterial exhibiting on one side thereof a plurality of discrete raisedportions, said discrete raised portions defining a continuous network ofchannels, said channels defining a void region adjacent said topsheet ofsaid sanitary napkin; wherein the plurality of discrete raised portionsand the continuous network of channels defines intermediate areas oflocalized reductions in web thickness, the intermediate areas having asubstantially different density or basis weight than the plurality ofdiscrete raised portions or the continuous network of channels andwherein the plurality of discrete raised portions are rib-like elements;said discrete raised portions defining an array of spaced,diamond-shaped regions or an array of spaced, circularly-shaped regions;and wherein one of the discrete raised regions has a density of about0.072 g/cc, and at least one channel has a density of about 0.093 g/cc.